Wednesday, December 12, 2012

Nest Thermostat Heating Issues

Problem

Alright, so I absolutely love the Nest - as it seems every Nest owner does. I was using it all leisurely during the summer and enjoying all of its benefits - but then when winter came - my Nest starting wigging out.

I thought originally it might have been my setup at my condo. My condo is one of those buildings where it's either "COOL" or "HEAT" on. Not both. So at one point in the winter, the building switched the heat on.

Now, even with my old thermostat - it's one of those on/off dealies. So if my thermostat was set to cool - the heat would actually turn on when the thermostat was "Cooling". But that's a separate issue. This is true of all thermostats for these types of buildings.

No - the issue that I was having separate. When I switched to heating, on the Nest - and when I set it to temperature that was higher than the current room temperature - the Nest should have started heating my place right?

Wrong.

Here's what happened (ie. the symptoms in case you're having the same issue)

Setup

Nest V1

Electric Forced Air Furnace

Wires: RH, Y1, W1, G

Symptons

The Nest was in "HEAT" mode

I set the Nest to a temperature hotter than the current temperature to engage heating

The display would show "Heating" for about 2 seconds, and then go to "Delayed for 3:00 Minutes". My fan would kick on for a bit, but that was it.

After the 3:00 minutes, same thing would happen "Heating" for about 2 seconds, and then back into "Delayed for 3:00 Minutes"

Here's the telltale sign - just after "Heating" for about 2 seconds, and just before "Delayed for 3:00 Minutes", the little green LED in the sensor area would blink (this should have been a sign to me).

So it would end up in the endless loop of "Heating" for about 2 seconds, and "Delayed for 3:00 Minutes" with that green LED flashing.

I called Nest Support - and it turns out it was a Voltage issue. Even though I was getting good voltage readings, there was an issue.

How to solve it?

I'm not taking any liability for this - and you should probably call Nest support - but you can try the follwing.

Temporary Work-Around

This has actually become my permanent work-around, because I don't feel like re-wiring my condo. The work-around is to UNPLUG THE COOLING "Y1" WIRE from the Nest during Heating seasons like Winter - so you just have RH, W1, and G. This apparently reduces the load or something. This works perfectly for me. I just have to unplug the wire/plug it back in once a year.

Permanent Fix

Nest support told me to run a wire from the furnace board's "Common" terminal to the "C" terminal on the Nest. Basically you need a common wire. However, I didn't have any extra wires long enough in my setup to do this.

I was having same symptoms on a nest v2 (flashing green light, "delay for x" messages). I removed my ac wires y1 and y2 (during winter) and reattached the base. Problem solved and heat returned. I also don't have a C wire hooked up, but will look into that.

Interesting that this happened to me tonight, right AFTER I added common 24VAC wire. Prior to this I had only a 2-wire (red/white) heat-only system. During months with little to no heat the Nest (V2) battery would die. While remodelling the living room we pulled a new cable that included a blue common wire. Tonight I hooked it up for the first time and had this same problem. Removed the common wire and it started working again. My suspicion is a reversed polarity on the red and white wires but I haven't verified yet.

Actually - it was not "reversed polarity" (meaning that the red/white wires crossed between furnace and nest - there's a junction box in my house - don't ask) but in fact the electrician (not HVAC tech - let that be a lesson) had hooked the blue wire to a 24 VAC constant terminal on the control board instead of a common terminal. So when the heat turned on, the voltage dropped. Moving the blue wire to the actual "common" terminal on the control board fixed the issue.

Wow! thanks for this post - this was the exact problem i had. 2 HVAC tech visits and I finally decided to google the issue. Never had this problem last year... I was able to connect a spare wire to the C connection as suggested. Thanks again.

I have a nest V2 and woke up to the same problem on the coldest day of the year in Denver at -1! It would say heating for 2 seconds, and then heating delayed. I removed the Y1 wire, reattached the base, and I have heat back. Thank you so much for posting this!

I've had my Nest 3rd gen for about three weeks now. The first two weeks it operated great. Now this week all sorts of issues. Low battery, disconnecting from internet. I charged it and it worked for about three days. Same thing today. I charged it and now I'm having the same issue you described.

Must be a low voltage issue. It's pulling about 3.7v from the wires. I don't have a common wire so will have to look into that.

A follow up to my January 20, 2017 post. It turned out I needed a common wire. Luckily I had one in the wall already and only had to strip the ends and hook it up to my control board. That took care of the issues.

You can tell you have a power issues if under technical info on the nest your VIN and VOC numbers are widely different and you don't have a LIN of 200 mA. Before the common wire my numbers were VOC 38v, VIN 9v, LIN 20mA. Now they are 38v, 38v, and 200mA.

THANK YOU! After 2 service calls in the last month (both during which we were told the furnace is completely fine) your article solved our heat issue! As soon as we unplugged the Y1 wire, our heat has been clicking right on!

THANK YOU!!!! Coldest day of season here at 4 degrees and this problem pops up. We've had the Nest for over a year with no issues. I went to store and bought another unit and had the same issue then I read your post and viola - we have heat! Thank you, thank you, thank you. Pretty garbage that Nest doesn't have this posted prominently on their site. I'm moving to something else as soon as weather breaks. I need dependability.

Thank you so very much for this valuable post. I had the exact problem and it became very cold in the house while we were sleeping, so much that the low temp woke us up. While waiting for a very long time on the phone to get some help from Nest tech support (at 6 AM I was on hold for 45 min.) I found your post and disconnected the Y wire (just pulled the thermostat out and saw the wires - very easy). Now at least it does not delays the heating. Let's hope my house will now warm up. I can see it is working. Thank you again.